This application relates to and incorporates herein by reference Japanese Patent Applications No. 11-223974 and No. 11-223987, both being filed on Aug. 6, 1999.
1. Field of the Invention
The present invention relates to a valve timing adjusting apparatus for changing the operation timing (valve timing) of a suction valve and/or an exhaust valve of an internal combustion engine.
2. Related Art
In a vane type valve timing adjusting apparatus, a camshaft is driven by means of a timing pulley, a chain sprocket, or the like that is rotated synchronously with a crankshaft of an engine. Thus, the valve timing of a suction valve and/or an exhaust valve is hydraulically controlled based on the phase difference of relative rotation between the timing pulley or chain sprocket and a camshaft.
In the case of such a vane type valve timing apparatus that uses working fluid, a load torque that fluctuates between positive side and negative side that is caused by driving the suction valve and/or the exhaust valve is exerted on the camshaft. For example, in the state that the working fluid is not supplied sufficiently as in the engine cranking at the starting of an engine, a vane member swings toward a housing member that accommodates the vane member, and generates hammering sound due to collision between the housing member and the vane member.
It is therefore proposed that a stopper piston fits a housing member when a camshaft is positioned intermediate between the most retarded angle and the most advanced angle with respect to the crankshaft to control the relative rotation of the camshaft with respect to the crankshaft. The engine is started with the camshaft being at the intermediate position between the most retarded angle and the most advanced angle. That is, the engine is thereby started in the state that the camshaft is located at the preferable position with respect to the crankshaft.
However, a force exerted on the stopper piston to be fitted with an fitting bore is only the urging force of a spring, it is difficult to fit the stopper piston in the fitting bore within a short time. Furthermore, in the case that a hydraulic pressure for maintaining the unrestricted state in which a contact portion is disengaged from the fitting bore is low, the stopper piston jumps out to the fitting bore side due to the urging force of the spring during the phase control for rotating the vane member relatively to the housing member. As a result the stopper piston can be caught in the fitting bore.
It is an object of the present invention to provide a valve timing adjusting apparatus for enabling an engine starting promptly while minimizing hammering sound.
It is another object of the present invention to provide a valve timing adjusting apparatus for preventing a constraint member from being constrained during a phase control.
According to a valve timing adjusting apparatus of the present invention, a constraint member is provided for constraining the relative rotation of a driven side rotor with respect to a driving side rotor when the driven side rotor is positioned at the intermediate position between the most retarded angle and the most advanced angle with respect to the driving side rotor is provided. By constraining the relative rotation of the driven side rotor with respect to the driving side rotor at the intermediate position, failure in starting an engine is reduced thus minimizing noxious exhaust gas.
In addition to release of constraint state associated with a contact portion and a contact receiving portion by means of the first working fluid pressure, the contact portion is displaced in the direction to be brought into contact with the contact receiving portion by means of the second working fluid pressure. For example, the first working fluid pressure that acts on the contact portion is reduced and the second working fluid pressure is increased when the engine is to be stopped. As a result, the contact portion is surely brought into contact with the contact receiving portion at the intermediate position. Thereby, the engine is surely started in a short time.
Furthermore, by reducing the first working fluid pressure that acts on the contact portion and by increasing the second working fluid pressure when the engine is to be started, the contact portion is held in contact with the contacted portion at the intermediate position. Because the intermediate phase can be held during cranking when the engine is to be started, the engine can be started surely in a short time.